There's only one MLB you can substitute for the 933MHz one: the 1064MHz (aka 1.07GHz or 1GHz) board from the same generation iBook G4. This board, like the 933MHz, has 128MB RAM built-in. The next generation iBook G4 also included a 1GHz MLB model, but that MLB has 256MB RAM on it, and due to a couple slight design differences, will not install in the originally 933MHz model. Nor will any later model.

(I am in fact doing just this upgrade: putting a 1GHz MLB into an iBook G4 whose original 933MHz board had died. I first got a 1GHz board from the next generation by mistake, and found it wouldn't install. So I've learned all about the fine points of this particular upgrade.)

[quote|HandyMac]There's only one MLB you can substitute for the 933MHz one: the 1064MHz (aka 1.07GHz or 1GHz) board from the '''same generation''' iBook G4. This board, like the 933MHz, has 128MB RAM built-in. The next generation iBook G4 also included a 1GHz MLB model, but that MLB has 256MB RAM on it, and due to a couple slight design differences, will not install in the originally 933MHz model. Nor will any later model. (I am in fact doing just this upgrade: putting a 1GHz MLB into an iBook G4 whose original 933MHz board had died. I first got a 1GHz board from the next generation by mistake, and found it wouldn't install. So I've learned all about the fine points of this particular upgrade.)[/quote]